1. Field of the Invention:
The present invention relates to a webbing lock apparatus for use in a seatbelt system designed to protect an occupant of a vehicle when an emergency situation of the vehicle occurs, the apparatus being adapted to prevent the occupant restraining webbing of the seatbelt system from moving longitudinally in an emergency situation of the vehicle.
2. Description of the Prior Art:
A typical seatbelt system of the type described above is arranged such that the occupant restraining webbing is automatically wound up into a webbing retractor when it is not used, and can be pulled out with a relatively small force when it is to be used. When fastened to the body of an occupant, the webbing does not restrict the movement of his body, but when a vehicular emergency occurs, the webbing is prevented from moving longitudinally, thus restricting the movement of the body of the occupant reliably, and protecting the occupant from injury. For this purpose, a conventional emergency lock apparatus employed in the seatbelt system has an arrangement such that one end portion of the webbing is wound up on a webbing take-up shaft with a ratchet wheel secured thereto, and when a vehicular emergency situation occurs, the pendulum of an inertia-type lock mechanism, which swings in response to gravitational acceleration, activates a pawl so as to engage with a tooth of the ratchet wheel, thereby stopping the wind-off of the webbing.
However, when this type of conventional emergency lock apparatus is employed in an automatic seatbelt system which enables an occupant to be automatically fastened by the webbing when he enters the vehicle and seats himself in the seat, it is necessary for the length of the webbing to be increased from the viewpoint of the mechanism of the automatic seatbelt system, which means that the diameter of the roll of webbing wound up on the take-up shaft is increased. In consequence, even when the rotation of the webbing take-up shaft is suspended by the operation of the inertia-type lock mechanism in the emergency situation of the vehicle, situation, the portion of the webbing wound on the take-up shaft in layers is tightened by the force of inertia acting on the body of the occupant, and the extra amount by which the webbing is undesirably wound off increases correspondingly.
To prevent the webbing from being undesirably wound off, one type of webbing lock apparatus has already been proposed in which the portion of the webbing unwound from the webbing take-up shaft is clamped by a pair of lock members. However, in this type of conventional webbing lock apparatus, the webbing must be passed over a plurality of rollers in order to pass the webbing through the area between the lock members. As a result, the movement of the webbing when it is wound in and out in normal use is undesirably retarded by means of the friction occurring between the webbing and the rollers.